I have two boxes, Box 1 hase a drop down selection with the following ratings: Exceptional, Very Good, Marginal, Unsatisfactory. I need to express the rating as a numerical value (4, 3, 2, 1) in an adjacent second field.

Here is the script I am trying to use but i recieve an error message: SyntaxError:missing) after condition 6: at line 7. What am I doing wrong?

var RB1 = this.getField("RatingBox1").value;

if (RB1 = Exceptional) {

    event.value = "4";

}

else if (RB1 = Very Good) {

    event.value = "3";

}

else if (RB1 = Satisfactory) {

    event.value = "2";

}

else if (RB1 = Marginal) {

    event.value = "1";

}

else if (RB1 = Unsatisfactory) {

    event.value = "0";

}

else if (RB1 = N/A) {

    event.value = "0";

}

if (isNaN(RB1) || RB1 === "") {

    event.value = "";

}